Mixing-mill for rubber



- 3 Sheets-Sheet 1. E. F.- BRAGG. MIXING MILL FOR RUBBER.

Patented Deo. 4, 1894.

(No Model.) 3 Sheets-Shet 2 HERR-AGG. MIXING MILL FOB. RUBBER.

PatentedDeo. 4, 1894.

No. 530,157, A

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amas PETERS oo.. morauwo., vlmsumamu u a (X oooooo f3 sssssss sheet 3.E. F. BRAGG. f j MIXIN LLLLLLLLLLLLL R.

Patented Deo. 4, 1894.

j y UNITED STATESl PATENT OFFICE.

MIXING-MILL FOR RUBBER.

SPECIFICATION forming part of Letters Patent No. 530,157, dated December4, 1894.

l APPHGOD filed November 15, 1893. Serial No. 490,974. (No mod el.) l

To all whom it may concern.-

Be it known that I, EDWARD F. BRAGG, of Boston, county of Suffolk, Stateof Massachusetts, have invented an Improvement in Mixing-Mills forRubber, of which the following description, in connection with theaccompanying drawings, is a specification, like letters on the drawingsrepresenting like parts.

Mixing mills for rubber, and like material, as commonly constructed,contain two cylindrical rolls driven in opposite directions, one at aspeed considerably in excess of the other, said rolls being rotatedusually at speeds respectively of about eight and fifteen rotations perminute. The crude rubber is passed loetween these rolls, it clinging tothe slow one, the foreign substance or compound with which the rubber isto be mixed being de posited between the rolls or upon the rubbervclinging to the slow roll and thereby thoroughly worked into and mixedwith the rubber.

It is impossible for all of the compound to be taken up at once, and itis therefore customary to provide an endless traveling apron to catchsuch portion or portions of the compound as may escape unmixed frombetween Ayoke pivoted in the frame of the machine,

and held by hooks, cords or other inflexible fastening devices in properposition to cause the apron to hug one of the rolls, the fasteningdevices being released when necessary' to permit the said yoke andmovable roller tQbe thrown down away from the rolls in order that therubber thereon may be removed. Again, it Vhas been customary to so mountthis endless carrier or apron that it runs in contact with the faster ofthe two rolls, the rubber and compound as before stated cling-- ing tothe slower roll.

Thisinvention has for its obj ect to improve mills of vthe class abovedescribed, whereby the capacity of the mill andthe thoroughness of themixture ot' the compound with the pure rubber are increased, and theoperation and control of the mill made more convenient andv `will behereinafter described.

My invention also consists in pivoting the roller carrier by which theendless apron is thrown'against the roll in such manner that when 'inits position against said roll, itstands at one side its dead center,whereby the tension alone of, theapron is sufficient to automaticallyretain 4the said carrier in such position. One of the other rollers,about which the said apron passes, is made to yieldby means ot' suitablesprings, to enable the said carrier and its roller to be moved from oneto another of its positions past the intermediate dead center and toexert the proper tension upon the apron to retain the carrier in itsposition against the roll as described; also to permit the apron toadjust itself to the in-v creasing diametei of the layer of rubber orvmaterial upon the roll as the said layer thickens by introduction ofthe foreign substance or compound. 4

My inventionalso comprehends various details of construction to be morefully herein- :after described and set forth in the claims, yone ofwhich consists in providing brushes to sweep or brush the compound fromthe endless fapron upon the mixing roll, and another in providing theapron with a rib running iu suitable annular grooves in the rollers, toprevent the apron creeping laterally in either direction.

ln the drawings, Figure l represents,in end view, partially broken away,one form of rubber mixing mill embodying my invention; Fig. 2, avertical section of the same taken on the dotted line w-m, Fig. 1; Fig.3,aper spective detail showing the rib upon the apron; Figs. 4 and lla,sectional detail and partial top Views respectively, showing thepreferred construction of the brushes for cleaning the apron; Fig. 5, across section detail showing one of the boxes for the yielding roller;Fig. 5', a detail showing top of one of are provided with suitablehorizontal guideways to receive the boxes a, a, for the journals of themain rolls B and B', cylindrical in shape and of any suitable or desiredconstruction, they being provided with suitable means for cooling,which, not constituting an essential part of this invention, is neithershown nor described.

The journal boxes for the roll B are shown as stationary, while theboxes for the roll B' are made to slide in the horizontal guidewaysreferred to and maintained in adjusted position, by the usual set screwsa', a.

In Fig. l s represents a main driving shaft provided with a spur wheel sin mesh with and driving the larger spur wheel s2, shown as fast uponone of the end journals of the roll B, the two rolls being gearedtogether at.

the opposite end of the machine by spur wheels .s3 and s4, shown indotted lines Fig. 2, and of such relative diameters that the speed ofrotation of the roll B shall be preferably about double that of the rollB', the relative speeds of the two rolls in usual practice being fteenrotations per minute for the roll B and eight for the roll B. It isevident, however, that the relative speed of rotation of the two rollsmay be varied to meet the various requirements, and that any suitabledriving mechanism other than that herein shown may, so far as thisinvention is concerned, be employed.

In accordance with one partof this present invention, I provide anendless apron C, the same being passed about three rollers c, c', andc2, the roller c being mounted in suitable fixed bearings c3 on thefront of the frame, as shown. The roller c', as herein shown, is mountedin suitable journal boxes c4, shown in dotted lines Fig. 2, the saidboxes being fitted to slide on suitable guide ribs c5, see Fig. 5,formed upon brackets c6 bolted or otherwise secured to the rear of theend frames, said boxes being drawn rearwardly by means of suitablesprings, shown as closecoiled springs c7 connected at one of their endsto the said boxes, and at their opposite ends to the blocks c threadedto receive the screws c8 loosely mounted in suitable bearings o9 on thesaid brackets and provided with proper means for adjustment shown ashand Wheels am. The roller c2 is `journaled at its opposite ends in theside armsd of a yoke D, said side arms as herein shown being provided attheir lower ends with roller or other suitable studs d shown in dottedlines Fig. 2, which enter and are adapted to move in the elliptical orcam-shaped openings e in the cam plates e',

at either end of the machine and bolted or otherwise securedto theinueradjacent faces of the end frames.

The top bar d2 of the yoke D is shown as a substantiallysemi-cylindrical member, bolted or otherwise secured at its ends to theinturned upper ends cl3 of the side arms d, said top bar being providedwith conveniently located handles d4 shown as arranged comparativelynear each other, in practice about eighteen inches apart, instead ofbeing arranged at the extreme ends of the yoke as is the usual practice.

In the full line position Fig. 2, it will be seen that the movableroller c2 is thrown to the left past the dead centerline drawnvertically through the fulcrum d', the tension of the apron created bythe springs c7 at the rear of the machine acting to retain the saidroller c2 and its yoke in the position shown with the apron in closecontact with the roll B without the use of any fastening devices toretain said yoke in such position. When, however, it is necessary tothrow the yoke down and away from the roll B for any purpose, theoperator grasps the handles (Z4 and draws the yoke to the right Fig. 2about d as a fulcru m, the said fulcrum at the same time sliding alongin the cam openings e. into its dotted position, to enable the said.roller c2 to more readily pass the dead center point, the tension uponthe apron and gravity thereafter operating to throw the said roller andits yoke away from the roll B' and down into its dotted position Fig. 2.The springs c7 which permit the yielding roller c to slide bodily towardthe front of the machine, enable the apron to also move toward the frontof the machine in order that the roller c2 may rise and pass the deadcenter line, which would be impossible if both rollers c and c werefixed, without straining the apron.

The movement of the apron bodily toward the front of the machine and thesliding movement of the roller c is reduced to a minimum by providingthe sliding fulcrum d for the yoke D, for were the said fulcrum fixed,said yoke in swinging about said fulcrum from one to another side of itsdead centerline would take up and require a much greater length ofapron.

The apron C is preferably of a width equal to the length of the rolls B,B', and is provided in the present instance, with a single longitudinalrib c, which runs in grooves cl2 in the rollers c, c' and c2, whichprevent the apron creeping in either direction, although more than onerib may be employed if desired.

To brush any compound from the apron and to keep the vlatter alwaysclean, I have provided the top bar d2 of the yoke D with one or more,preferably a series of, independent brushes as E, see Fig. 4, which bearupon the apron as the latter moves through the yoke, said brushes Ebeing acted upon and pressed against the apron by means of suit- ICO IIC

g end of the roll. r

able springs as e2, I having herein'shown two4 such springs for eachbrush, theV ends. of vadjacent brushes being overlapped as at e3 Fig. 4ato thereby break jointsyand presentas it were a single continuous brush.

H, H, represent lateral guide plates shaped to enter between the rollsat the top of the mill to prevent the rubber working out at the ends ofthe machine.

As herein shown and preferably, the guides H, H, are each fitted to andadapted to slide vertically in suitable brackets h, h, bolted orotherwise secured to the end frames, said brackets being provided withadjusting screws h', by which to effect vertical adjustment of saidguides.

To prevent the compound working off the ends of the roll B', I haveprovided said roll with end collars b, said collars, as herein shown,being formed in segments preferably two in number bolted togetherbybolts b shown in dotted lines Fig. 2, embracing the M represents atable arranged beneath the machine to catch and support the-endlessapron when the latter is slackened by throw ing back of thev yoke. f Theoperation of the mill is as follows:-

The screws a' are first slackened, to permit the rolls B and B' toseparate sufficiently to draw in the crude rubber deposited in lumps orlarge pieces in the space between the rolls from the top, said rubberbeing drawn between the rolls and worked into a sleeve or layersurrounding and hugging the slow roll B', as shown by the heavyv blackline Fig 6r. During this time the yoke D is maintained in itsl dottedposition Fig. 2 with the apron removed from the roll. Afterthe rubberhas been rolled into a proper layer about the roll B', and the rollspressed together by means of the screws o.' until the said layer orsleeve of rubber is of suitable thickness, the operator throws the yokeinto its full line position Fig. 2, in which position it isautomatically held, without fastening devices, by the springs c7, withthe endless apron C in contact with the rubber layer or sleevesurrounding the rotating roll B', the said apron being thereby caused totravel in the same direction as said roll. See arrows Fig. 2. Thecompound or foreign substance or material with which the rubber is to bemixed is then thrown in between the oppositely rotating rolls and ismore or less wprked into the rubber at the pinch between the rolls, theexcess of compound which cannot be taken up at once, working or droppingthrough upon the traveling apron C beneath, which carries it around incontact with the layer of rubber upon the roll, and again deposits itupon the top of the said roll to bc passed once more between the rollsand worked into the rubber, this operationbeing repeated until all ofthe compound is thoroughly worked into the rubber.

The brushes E act to brush all the compound carried up by the endlessapron off onto the rubber coated roll. vAs the compound is worked intothe rubber, the space between the rolls remaining fixed, the coating orsleeve surrounding the roll B' is necessarilylengthcned, :owing to theyadditional material incorthe said sleeve so lengthened tending to droopor sag away from the roll at the under side. The traveling apron howeverbeing in contact with the sagging sleeve of rubber takes the sag orslack along with it to the upper side of the roll as in Fig. '7, when itis lapped over'upon itself as shown in Fig. 8, so that it passes throughthe pinch between the rollsl in three thicknesses instead of one as inmachines as now constructed, the three thicknesses being thoroughlyworked `together linto a single thickness. This folding and doublingoperation takes place at each two or three rotations of .the roll B',according to the quantity of 'compound worked into the rubber and therapidity with which it is incorporated therewith, dependent more or lessupon lthe separation of the rolls, said folding or doubling operation,due solely to running the endless apron on the slow roll B' to whichtherubber adheres, being of the utmost importance as it enables thecompound to be worked into the rubber in much less time than hashitherto been possible. This is for the reason that when the compound isrolled upon the rubber it ,mixes with the latter at Iirst only for ashort depth in from the outer face of the rubber, that portion of therubber next the roll receiving at first little or .none of the compound.As the outer surface of the rubber layer becomes more or less filledwith the compound at the very first, decreasing its richness, itsability to take compound correspondingly lessens, rendering it moredifficult for the rolls to force the compound thereafter through to theinner and richer portions of the said layer; but by folding over ordoubling the layer every few rotations of the roll, as in the presentinvention, the richer outer portions of the rubber layer which receiveat iirst little or none of the compound, are interposed between andworked into adjacent faces of the layer which have at first received thecompound, the latter being thereby introduced at different lines in thethickness of the layer and more thoroughly and quickly incorporatedtherewith. This is illustrated in Fig. 9 where the heavily shadedportions of the rubber layer represent the portions which have receivedthe compound, the lighter shaded portions representing the pure or richrubber which has yet to receive the compound. It will beseen from thisgure that by the folding operation described the rich portions areinterposed between portions which have already received compound,thereby making it possible to more thoroughly distribute the compoundthrough the entire thickness of the layer.

IOC

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In practice I have found that by running the apron on the slow roll, thecompound may be incorporated with the rubber in at least one quarterless time than when the apron is run on the fast roll.

The spring c7 permits the apron to move toward and from theperipheralsurface of the roll B according as the rubber layer thereon isof greater or less thickness, thereby avoiding injury to the apronusually caused by stretching of the same beyond its normal length.

This invention is not restricted to the particular construction of millherein used to illustrate this invention, nor is the invention otherwiserestricted to the particular construction and arrangement of partsshown, for while I consider the construction shown an excellent one, yetthe same may be varied more or less without departing from the spiritand scope of the invention.

Having described my invention, what I claim, and desire to securebyLetters Patent, 1s-

1. In a mixing mill for rubber and like material,two rolls, and means torotate the same in opposite directions, one at a higher speed than theother whereby the material adheres to thelatter, combined with anendless apron moving in contact with and in the same direction as theslow moving roll or the material thereon, to act upon said material,substantially as described.

2. In a mixing mill for rubber and the like, two rolls,` and means torotate the same, combined with an endless apron and movable and yieldingrollers over which said apron is passed, the former movable toward andfrom one of said rolls and the latter yielding to permit such movement,substantially as described.

3. In a mixing mill for rubber and like material, two rolls, and meansto rotate thesame, combined with an""endless apron adapted to travel incontact with one of said rolls or the layer of material thereupon, andtwo or more rollers over which said apron travels, and springs to retainone of said rollers in normal position whereby said roller may yield toaccommodate changes in position of said apron, substantially asdescribed.

4. In a mixing mill for rubber and the like, two rolls and means torotate the same, combined with an endless apron; a yoke; a cam openingiu which the fulcrum thereof is movable; a roller carried by said yokeand over which said apronis passed; and a yielding roller also for saidapron whereby the said apron is enabled to change its position to permitsaid yoke to be moved from one to another side of its dead center line,substantially as described.

' 5. In a mixing mill for rubber and the like, a frame; two rolls andmeans to rotate the same, combined with an endless apron; a pivotedyoke; a roller carried thereby, and a roller on said frame, over whichsaid apron is passed; and one or more brushes on and movable with saidyoke to sweep said apron, substantially as described.

` In testimony whereof I have signed my name to this specification inthe presence of two subscribing witnesses.

EDWARD F. BRAGG.

Witnesses:

FREDERICK L. EMERY, EMMA J. BENNETT.

